I Really Blew It!!!
- Thread starter KingBubba
- Start date
KingBubba
"Too Much Stuff"
I did find the 2S versions when I googled the part #. I was not sure if that was the same part. I'm pleased to have you confirm that it is the same. Dave, I got your email, Thanks for finding them for me. There appear to be two bad ones but I would be inclined to replace all since I'm at it. This amp is worth it to me but I would only do it if it was going to buy me any benefit. I'd keep the others for spares. Any opinions about this, would replacing all transistors benefit me or would it be a waste of money? Also is the silicone type thermal paste that I have appropriate for these transistors?
Well the amps are based on two pairs of each it probably would be a good idea to replace all 4 on the bad channel and if you could swing it get at least another 2 pairs spare for the other channel,just in case "god forbid". If the thermal grease you have is the white zinc oxide varity yes thats fine.Are there any mica insulators? If so be careful with them so as to reuse them,those transistors are rather oddball shape and my be tough to find new insulators for.
Dave
Dave
avionic said:Hmmm,Discontinued 1984... probably not new stock...But old stock is better than no stock.Just one of the issues you have to deal with when repairing vintage equipment....Parts is Parts...
Dave
Like I said they are probably New Old Stock (old but never been used).
Which is a good thing because if they were made recently they would more
than likely be fakes.
I will second that,
Definitely replace all four in the blown channel.
KingBubba
"Too Much Stuff"
The mica has been carefully tucked away in a nice neat little box with the bolts. Yes the silicone I have is indeed the white stuff. I found a place in Florida that might have the transistors. I will call them tomorrow and see if they can beat Mr. Ebay Parts person. I'll be home all day tomorrow so I will have the time to deal with a search. Thanks for the input.
Detailman
Addicted to tweaking
Hey Bubba
Since you live in Fla have you checked Skycrafters in Orlando. Don't know if you are familiar with them but they are 10 seconds off I4 in Winter Park.
Don't remember the exit but they carry all kinds of stuff and they do have a website but I can't seem to find the link.
Shouldn't be too far from you. They have all kinds of electronics and usually pretty cheap.
Since you live in Fla have you checked Skycrafters in Orlando. Don't know if you are familiar with them but they are 10 seconds off I4 in Winter Park.
Don't remember the exit but they carry all kinds of stuff and they do have a website but I can't seem to find the link.
Shouldn't be too far from you. They have all kinds of electronics and usually pretty cheap.
KingBubba
"Too Much Stuff"
Just an update for those of you that might be following this thread, Avionic, Dave, was kind enough to allow me to call him at home tonight. He verified for me that I had indeed blown 1 pnp and 1 npn transistor. Because it was one of each type, the amp was shorted to both the + and the - rails and that is why both fuses were blowing. He also advised me of where I need to test on the boards before attempting to apply power to the unit with the outputs removed. The TPs tested as if they were attached to a cap and he assured me that because of the center tap transformer, that would be normal. After our conversation I plugged in the amp with no outputs and it did not blow any fuses and remained dormant. The relay did not kick on. At this point I am not sure if that is a good thing or a bad thing, but I think it means I'm okay at this point.
This adventure has at least given me a a good solid chance to see the troubleshooting process for this type of problem. I wish I had not screwed up, but at least I am learning from my mistake. I'll keep this thread alive after I have dug up the transistors I need.
I do have one question that still lingers about this event. When I was retesting the second side after the amp had warmed up for 1/2 hour, the first TP reading was in spec at 30mv but the second TP was out of spec by 15mv. The manual said +-10mv was acceptable, not 15mv. What would have been the cause of that kind of over voltage aberration. I did not get the impression I was going to be able to adjust it out. This has me puzzled and I think that I may be finding that it will reappear after I get back to setting the bias again. Any guesses on this?
This adventure has at least given me a a good solid chance to see the troubleshooting process for this type of problem. I wish I had not screwed up, but at least I am learning from my mistake. I'll keep this thread alive after I have dug up the transistors I need.
I do have one question that still lingers about this event. When I was retesting the second side after the amp had warmed up for 1/2 hour, the first TP reading was in spec at 30mv but the second TP was out of spec by 15mv. The manual said +-10mv was acceptable, not 15mv. What would have been the cause of that kind of over voltage aberration. I did not get the impression I was going to be able to adjust it out. This has me puzzled and I think that I may be finding that it will reappear after I get back to setting the bias again. Any guesses on this?
There are likely more bad components, or else the protection relay would have engaged. You need to measure the output line of the amp to check for excessive offset, which will tell you if you got more troubleshooting to do.KingBubba said:
No guesses, since you don't tell us what you were measuring.